Currently, it is relatively expensive, time consuming and difficult to install cellular networks. The network installation is especially problematic in highly populated urban areas.
Cellular systems use base stations to establish an RF link between each user in the cell and the cellular wired network. These base stations use a relatively high transmit power, to overcome propagation losses in order to achieve a reliable link. This high RF power, however, may be harmful to people nearby. Moreover, it may interfere with other electronic equipment. These may be part of the reasons why people object to the installation of base stations in populated areas.
In highly populated areas there is a need for more base stations, more closely located to each other. As more users are to be served in a specific area, the cells are made smaller, and more base stations have to be installed.
Therefore, the objection of the public to the installation of additional base stations is a serious impediment to the development of a cellular network.
Moreover, in highly populated areas the real estate is usually expensive. It requires a large investment to install base stations in these areas and to install the wiring as required. Once the base stations are installed, it may be required to service them.
One can appreciate the high maintenance cost for a multitude of base stations located in a highly populated urban area.
Heretofore, a large distributed network required a plurality of large switchboards to make all the required connections. As the number of cells and users increase, the number and complexity of switchboards increases as well. There is a large number of concurrent calls that have to be supported. This further increases the cost of setting up and operating a cellular network.
It is an objective of the present invention to facilitate the installation and expansion of distributed cellular networks, especially in highly populated urban areas.
Another problem in cellular systems is the relatively high transmitted power of the mobile phones. The transmit antenna is close to the user's head, and the RF radiation may have undesirable effects.
As the distance to a base station increases, the mobile transmitter has to transmit at a higher power. Thus, from the radiation hazard viewpoint, it would be desirable to have more base stations, more closely related. This would allow transmission at lower power. There are problems to adding base stations, however, as detailed above.
It is another objective of the present invention to achieve a reduction in the mobile phone transmit power, by using more base stations that are more closely located to each other.